The present invention relates generally to a seam structure for a papermaking fabric woven endless.
Papermaking fabrics and particularly press fabrics have long used pintle seams as is illustrated in U.S. Pat. Nos. 4,737,241; 4,824,525; and 5,799,709. As shown, the pintle is normally of a larger diameter than the diameter of the transverse yarns. This requires that the loops be formed larger than the space required for a warp yarn in order to receive the pintle. Because of the pintle size, it is important that additional fiber be provided in the area of the seam to form additional cover to prevent undesirable markings on the paper. Another concern is that the endmost transverse yarns have a tendency to slip longitudinally into the area of the loop during use. This also causes unwanted markings on the paper.
Accordingly, it is an object of this invention, to provide a seam structure in which additional fibers are provided in the area of the seam.
Another object of the invention is a seam construction which utilizes additional multi-filament yarns outside of but adjacent the endmost transverse yarns of the fabric.
Another object of the invention is to provide a pintle seam structure which stabilizes the position of the endmost transverse yarns of the body portion of the fabric.
Another object of the invention is the provision of additional yarns adjacent the endmost transverse yarns of the fabric which interlace with and are exposed on both the support surface and the running surface.
Another object of the invention is the provision of a fabric structure capable of being needled to form a fiber cover over the area of the seam.
The instant invention is directed to a seamed endless papermaking fabric for use with papermaking machines which is formed with a machine contact surface and a paper support surface. The fabric includes a plurality of CMD (cross machine direction) yarns intermeshed with a plurality MD (machine direction yarns) in a selected intermeshing pattern. The MD yarns extend beyond the endmost of the CMD yarns at the opposed ends of the fabric forming a plurality of spaced seaming loops across each of these ends. The loops are adapted to be interleaved forming a channel which receives a pintle forming the seam forming the fabric endless. A first pair of additional yarns are intermeshed in a first intermeshing pattern repeat with the MD yarns outwardly of but adjacent the endmost CMD yarns at a first of the opposed ends of the fabric. A second pair of additional yarns are intermeshed in a second intermeshing pattern repeat with the MD yarns outwardly of and adjacent the CMD yarns at the second of the opposed ends of the fabric. These pairs of additional yarns are between the endmost CMD yarns and the pintle.
The first and second pairs of additional yarns and the MD yarns are interwoven in selected weave patterns while at least one of the first and second pairs of additional yarns interweaves with the MD yarns to appear primarily on the contact surface or they may be woven with the MD yarns to appear equally on the contact surface and the support surface.
The MD yarns are weft yarns and the additional yarns and the CMD yarns are warp yarns. The selected weave patterns repeat for the additional yarns on one of twenty-four and thirty-two picks. The CMD and MD yarns are preferably synthetic monofilament yarns while at least one of the first and second pairs of additional yarns are synthetic multi-filament yarns. Preferably all of the additional yarns are multi-filament synthetic yarns.
A seamed endless papermaking fabric for use on papermaking machines formed of a plurality of CMD (cross machine direction) yarns interwoven with a plurality of MD (machine direction) yarns in a selected weave pattern to form a contact surface and a support surface. The MD yarns extend beyond the endmost of the CMD yarns at opposed first and second ends of the fabric forming a plurality of spaced seaming loops across each end. These loops are adapted to interleaf and receive a pintle which forms the seam forming the fabric endless.
First and second pairs of additional yarns are interwoven in second and third selected weave patterns with the MD yarns outwardly of the endmost CMD yarns at the first and second ends. Each of the first and second yarns of each pair of additional yarns is interwoven with the MD yarns to appear on both the contact and support surfaces in each repeat of the second and third weave patterns. Each yarn of the first and second pair of additional yarns may appear equally on the contact surface and the support surface or each yarn of the first and second pairs of additional yarns may appear primarily on the support surface. Preferably, the additional yarns are synthetic multi-filament yarns, however, this is not necessary for both yarns of each pair. The second and third selected weave patterns of the additional yarns repeat on one of twenty-four and thirty-two picks.